In "Live Free or Die Hard," the fourth chapter in the high-octane action franchise, a mastermind cyber-criminal holds America hostage by wreaking havoc via the Internet. It's a great thriller, but could this imagined scenario ever happen in real life? According to recent history, it already has. The true crimes are as dramatic as anything Hollywood could imagine. See how an all-out cyber-attack on the U.S. is a very real possibility. Then meet the government officials and former hackers tasked with ensuring our digital space is safe.